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HDU 5154 Harry and Magical Computer bfs

2024-10-31 06:46:39   209人阅读

Harry and Magical Computer

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 499    Accepted Submission(s): 233


Problem Description
In reward of being yearly outstanding magic student, Harry gets a magical computer. When the computer begins to deal with a process, it will work until the ending of the processes. One day the computer got n processes to deal with. We number the processes from 1 to n. However there are some dependencies between some processes. When there exists a dependencies (a, b), it means process b must be finished before process a. By knowing all the m dependencies, Harry wants to know if the computer can finish all the n processes.
 

 

Input
There are several test cases, you should process to the end of file.
For each test case, there are two numbers n m on the first line, indicates the number processes and the number of dependencies. 1≤n≤100,1≤m≤10000
The next following m lines, each line contains two numbers a b, indicates a dependencies (a, b). 1≤a,b≤n
 

 

Output
Output one line for each test case.
If the computer can finish all the process print "YES" (Without quotes).
Else print "NO" (Without quotes).
 

 

Sample Input
3 23 12 13 33 22 11 3
 

 

Sample Output
YESNO

 

 

#include <cstdio>#include <cmath>#include <cstring>#include <ctime>#include <iostream>#include <algorithm>#include <set>#include <vector>#include <sstream>#include <queue>#include <typeinfo>#include <fstream>typedef long long ll;using namespace std;//freopen("D.in","r",stdin);//freopen("D.out","w",stdout);#define sspeed ios_base::sync_with_stdio(0);cin.tie(0)#define maxn 100001const int inf=0x7fffffff;   //无限大 int map[101][101];int vis[101];int flag[101];int main(){    int n,m;    while(cin>>n>>m)    {        memset(map,0,sizeof(map));        memset(vis,0,sizeof(vis));        memset(flag,0,sizeof(flag));        int a,b;        for(int i=0;i<m;i++)        {            cin>>a>>b;            map[b-1][a-1]=1;            flag[a-1]=1;        }        queue<int> q;        for(int i=0;i<n;i++)        {             if(flag[i]==0)            {                q.push(i);                vis[i]=1;            }        }        int now;        int next;        while(!q.empty())        {            now=q.front();            for(int i=0;i<n;i++)            {                if(map[now][i]==1)                {                    if(vis[i]==1)                        continue;                    q.push(i);                    vis[i]=1;                }            }            q.pop();        }        int flag1=0;        for(int i=0;i<n;i++)        {            if(vis[i]==0)            {                flag1=1;                break;            }        }        if(flag1==1)            cout<<"NO"<<endl;        else            cout<<"YES"<<endl;    }}

 

HDU 5154 Harry and Magical Computer bfs


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